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Discussion Starter · #1 ·
I have a 93 d150 with a remaned 318. First start of the day, it will fire right up and idle fine. I'm able to drive it for not even a mile and it dies on me. Then it won't fire back up unless I hold my foot to the floor. Even then it doesn't stay running. The truck has a new fuel pump and i did a fuel pressure test. When turning over it has about 39 lbs then it slowly looses pressure. It also has a new distributor. I pulled the plugs to see if i am getting spark and i am. I noticed that the plugs are jet black. The throttle body was also just cleaned. Does anyone have any idea what this could be?*
 

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Discussion Starter · #4 ·
Fuel pump and filter are brand new. Could it be an injector problem? Also what sensor controls my temp gauge on the dash?
 

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When the pump was changed, was the entire module changed, or just the pump within the module? Thinking maybe a fuel pressure regulator problem. I need to dig a bit. The early Mags didn't continuously operate at near 40psi. Rather, they ran at the pre-Mag pressure more near 15psi. Does yours fall off to that level and maintain, or contine to fall? Ruling out the fuel issue, I'd look at sensors or a vacuum issue. Was the intake plenum plate resealed? They can cause massive vacuum leaks, especially once warmed up. Beyond that it could be a bad MAP sensor, though they usually just flat out fail. Old ignition coils can initially fire an engine when cold, but shut down once hot.
 

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My bad, I thought this was a LA not a magnum. If it's dropping there is an issue somewhere. Need to find out if it stays running(pump) while the pressure drops or maybe the relay is cutting out.
 

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Probably have already solved it but have you dropped the fuel tank by chance and actually cleaned it out? I’m wondering if old rust and debris are settled in the bottom of the tank and quickly clog the line but settle over time hence the good start in the morning
 
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